Kate Middleton made a statement in a $1,590 dress made out of repurposed denim

• On Saturday, Kensington Palace announced that Kate Middleton, Prince William, and their kids recently met with "Planet Earth" narrator David Attenborough in the gardens of their home.
• For the occasion, the Duchess of Cambridge wore a midi denim dress from Gabriela Hearst that retailed for $1,590 before selling out at the time of writing.
• The dress is from Hearst's pre-fall 2020 collection and is made from repurposed denim.

Kate Middleton knows how to make a statement in just a simple look.

On Saturday, Kensington Palace shared three photos of the Duke and Duchess of Cambridge and their kids, Prince George, Princess Charlotte, and Prince Louis, meeting with "Planet Earth" narrator Sir David Attenborough in the gardens of their home.

Middleton wore a denim dress from Gabriela Hearst's pre-fall 2020 collection for the occasion. She paired the dress — made from repurposed denim, according to Vogue — with $465 navy-blue block heels from Emmy London.

The Duke and Duchess of Cambridge are delighted to share new photographs of their family with @DavidAttenborough. The photographs were taken earlier this week in the gardens of Kensington Palace, after The Duke and Sir David attended an outdoor screening of Sir David’s upcoming feature film ️ ‘David Attenborough: A Life On Our Planet’. With a shared passion for protecting the natural world, they continue to support one another in their missions to tackle some of the biggest environmental challenges our planet faces. This includes working together on The @EarthshotPrize the most prestigious global environment prize in history – further details of which will be shared in the coming weeks. When they met, Sir David gave Prince George a tooth from a giant shark the scientific name of which is carcharocles megalodon (‘big tooth’). Sir David found the tooth on a family holiday to Malta in the late 1960s, embedded in the island’s soft yellow limestone which was laid down during the Miocene period some 23 million years ago. Carcharocles is believed to have grown to 15 metres in length, which is about twice the length of the Great White, the largest shark alive today.

A post shared by Duke and Duchess of Cambridge (@kensingtonroyal) on Sep 26, 2020 at 2:30pm PDTSep 26, 2020 at 2:30pm PDT

The Marley belted denim midi shirt dress that Middleton wore was sold out at the time of writing, but it had a price tag of $1,590 on MatchesFashion.

In a blog post on the designer's website, Hearst says that the pre-fall line "is always one of the most sustainable collections that we do, because we work from sketches and swatches."

"We don't even develop one sample, because we have plenty of preexisting materials," she added.

Middleton's upcycled outfit subtly matched the theme of her family's meeting with Attenborough.

According to the Instagram caption of Kensington Palace's post, the focus of their discussion was their "shared passion for protecting the natural world" by tackling some of the environmental challenges the world is currently facing.

It's not the first time Middleton has worn sustainable fashion

In May, she wore a yellow printed dress from Raey, an in-house MatchesFashion brand that focuses on using low-impact materials and a supply chain that is traceable and responsible, according to a 2018 sustainability report from the brand.

The Duchess and the @NationalPortraitGallery are inviting the people of the UK to submit a #HoldStill2020 photographic portrait, which you have taken during these extraordinary times. The project focuses on three core themes: Helpers and Heroes. Your New Normal. Acts of Kindness. One hundred shortlisted portraits will feature in a gallery without walls – a one of a kind digital exhibition open to all this August. Submit your images through the link in bio to enter and share your portraits on Instagram by tagging @KensingtonRoyal #HoldStill2020 to be in with a chance to be featured on our channel throughout the project. #StayAtHome

A post shared by Duke and Duchess of Cambridge (@kensingtonroyal) on May 7, 2020 at 4:09am PDTMay 7, 2020 at 4:09am PDT

Middleton is also a longtime fan of Stella McCartney, who is known for never using leather or fur for her products.

Middleton's sister-in-law Meghan Markle is also a fan of McCartney, choosing to wear a dress by the designer for her wedding reception in 2018.

And like Middleton, Markle has incorporated sustainable brands into her wardrobe.

It's no secret that Markle loves to rewear her Rothy flats. The machine-washable shoes are made from materials including plastic water bottles and eco-friendly outsoles.

• Read more:
• 16 of Kate Middleton's best fall fashion looks
• Prince William, Kate Middleton, and their kids met David Attenborough, and Princess Charlotte's excitement was captured on camera
• Kate Middleton dressed down a pair of $38 trousers that were originally part of a suit by wearing them with white sneakers
• Kate Middleton wore a $13 Zara dress designed with a thigh-high slit during a Zoom call